The questions I answered

Saturday, July 2, 2011

A linear set of wires is given to you. The current in the wires is flowing perpendicular to the plane of paper and towards the reader. The set is infinitely long and the current flowing through the set is uniform and that is lambda amperes per unit width.We have to find out the magnetic field due to this current distribution.

We'll solve this problem by using Ampere's circuital law.

Since, current distribution is uniform, w can create a closed surface for any amount of width.

So, ABCD is the rectangular ampere's closed surface which has a width x. We'll do the calculation with respect to this closed surface. In the diagram, I have shown you the direction of magnetic field B. I found the direction using Fleming's Right Hand Rule. According to this rule, we have to place the thumb along the direction of current, then we have to open our palm and make a pushing movement. The direction along which the palm seems to knock will be the direction of magnetic field.

Now we are going to apply the Ampere's Circuital Law.

In 2 cases, B and dl are parallel to each other. So angle between them is 0 deg. Therefore cos 0 = 1.
In the other 2 cases, B and dl are perpendicular to each other. So angle between them is 90 deg. cos 90 = 0.

Therefore, out of the 4 results, 2 of them are not considered as they are equal to 0.

Food chains and webs not only describe the order in which organisms are eaten, but they also describe the _____.
flow of energy in an ecosystem
importance of the ecosystem
health of the ecosystem
animals that are all related

In the food chain, ____ can make their own food.
producers
primary consumers
secondary consumers
decomposers

What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle?

A point charge q = 5.0 µC is placed at each corner of an equilateral triangle with sides 0.20m in length.
A) What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle?
B) Is the magnitude of the electric field at the center of the triangle greater than, less than, or the same as the magnitude at the midpoint of a side? Explain.
please help me please.

Answer:

I have arranged the charges as above at the three vertices of equilateral triangle.

so according to the diagram, at any side of the triangle, fields of two charges will neutralize each other. So, only the field due to one remaining charge will be the net electric field.

In the above diagram, the red vector and the black vector neutralizes each other. So, only the violet vector remains.

So, the net electric field will be due to one charge only.

But, at the centre, all the field vectors from the individual charges will act. According to the diagram, they make an angle of 120 deg with each other. So, the net force becomes zero.

Tuesday, June 28, 2011

Which of the following are global environmental problems? Why?

a.The growth of human populationb.The furbish lousewort, a small flowering plant found in the state of Maine.It is so rare that it has been seen by few people and is considered endangeredc.The blue whale, listed as an endangered species under the us marine mammal protection act.d.A car that has air conditioninge.seriously polluted harbors and coastlines in major ocean ports

My answer:

a,d, e are environmental problems

The growth of human population

REduction of natural resourcesdeforestation to build homespollution

A car that has air conditioning

CFC released by it causes disruption of ozone layer.

seriously polluted harbors and coastlines in major ocean ports

Bacterias grow on the pollutant, reduces the oxygen level of water. Disrupt the aquatic ecosystem.

Sorry I can't copy the image on here so I put a link at the bottom of the page.
A picture with mass of 22.5 kg is supported by two wires. Find the tension in each cable.

When the picture is hanging from the wire, the wire makes an uneven V shape. The left part of the wire is T2 (tension 2) and the right wire is T1. The angle that the left wire makes with the ceiling is 60 degrees and the right wire makes a 30 degree angle as seen below.